Mounting an engine and gearbox

[Toolman]

Hi ,
Im at that point of mounting motor and gearbox , Im worried Ill mess it up , it may seem right at the time , but down the track when I actually get
to drive it and theres a vibration because I was not 100% up to speed with doing this ( or ever done it before ) .
Is it better to farm this out and get a pro to do it .
At the moment the mounts are loose that go on the front crossmember and the gearbox mount is also loose with no reference points for either ?
Am I panicking and should just mount it parallel to the chassis so everything clears and then fit a tailshaft ?

[Drewfus]

Firstly, with consideration to vibration issues, here's a user-friendly example of illustrating the importance of having the engine/trans. output shaft center-line parallel with the diff's third member pinion center-line.



Another thing to consider with the above is that ideally your universals don't like to have big angle variations between the input/output, typically most prefer to operate with a number between 3-6 degree's, so if you can imagine the center-lines of your engine, then the driveshaft, then going into the diff, whatever number you come up with at the front, ideally needs to be the same at the rear, and also somewhere between 3 and 6. The sky won't fall if it's a bigger variance (although service life of your uni's will be reduced), but it will shake the crap out of everything if they're not close at their typical service position.

There's other fitting elements to typically consider, although most on a case-by-case deal, and not really specific to driveline vibration. Graffiti do a good street-rod building book (although name escapes me at the moment) that help illustrate the basic elements to consider, which should cover most common concerns related.

Cheers,
Drewfus

[Toolman]

Thankyou Drewfus , maybe I can do it not as critical as I was thinking .

[toprodz]

Hey Toolman
This is the way I set up a motor and trans , normally I have no springs in the suspension and have struts in there place to make sure the chassis is at finished ride height. then dummy the motor and trans in place. if using a carburetted motor you will need to make the carb flange level in both directions, which in most cases, the crank will now be at 3 degrees. you will most likely find that the trans pan is pretty close to level as well, then fabricate your mounts to suit, if using a trans tube or similar I tend to jack the mount up a little higher than needed and this will allow for a little compression in the mounts with the complete weight of the motor on them
I hope this makes sense, if you have any queries, PM me your number and I can have a chat with you

[monte]

I have often wondered how things work out when you see some of these 4x4 beasts around ,some are actually raised lots with no change in the engine mounts ,like the unies are at all sorts of angles ,so do they vibrate or what ,we see lots of them up here in the bush cause its a big hobby with the younger folk and they dont seem to have any problem with driving them at speed .I recall years ago I was told by on old engineer that unies work correctly when they dont all line up ,but it seems that the information was not correct and now We see that people are saying that they should . Interesting subject this ,can we have some more thoughts on it

[FRANK BASILE]

Another method when doing a swap and the existing engine is in place. Take reference measurements from a fixed point left and right where the front damper centre is . As well as height from a crossmember or a fixed point below it . Do the same at the rear of the trans with the spline by using the floor tunnel etc . The second bit works well if the whole engine/trans assy s are the same length for original and replacement. Anyway the first bit does establish the crankshaft line to the diff .

[monte]

I checked out
Drewfus post there and that explains it perfectly to me .It appears that as long as the angles front and rear are the same it all works ,good stuff

[Drewfus]

I have often wondered how things work out when you see some of these 4x4 beasts around ,some are actually raised lots with no change in the engine mounts ,like the unies are at all sorts of angles ,so do they vibrate or what ,we see lots of them up here in the bush cause its a big hobby with the younger folk and they don't seem to have any problem with driving them at speed

Monte, short answer is that if the angle is outside the universals 'best' working range, then its service life will be shortened. Vibration is primarily induced by either 'out-of'balance' (just like spinning a rim and tyre that's not balanced correctly), or not having your input/output angles in sync like the video clip earlier. With regards to the 4x4 deal, the principals of physics still apply, but since the bulk of people use these at a lower rpm, they aren't as notable, service life isn't as long but most people will damage and replace their driveshafts, CV's and uni's more anyhow. Speed will make a notable difference, however vibration from out of balance 35" (and bigger) Bogger tyres on steel rims, and other influencing elements will make it hard to identify the influence of the driveshafts. The issue will still be there, just clouded with all the other things. Keep the rpm down, and you can get away with all sorts of 'bad' geometry, not very efficient or best practice, but achievable for a short duration. Just don't expect it to last, or be happy at speed.

Cheers,
Drewfus

[T1916]

Hi monte
Bit off the topic but in the early 90.s the issue of these high lift 4x4 was looked into by the insurance industry for the number of roll overs caused by the lose of control (bump steer.) Most of these vehicles had cross steer like a Rod and when lifted the angle of the drag link from the steering box to the opposite steering arm on the stub was no longer parallel to the axle. But was at a severe downward angle. Any up and down suspension movement had a severe bump steer effect on the steering. They started declining claims if the vehicle,s suspension was modified from stock height.


Cheers GT

[Tappet Head]

Time to revive an old thread, had a bit of a search and didn't really find anything.

Setting up my engine and box, its currently at 12 degrees negative, normally a north south engine is set at 3 to 4 degrees, I can get 4, to 12 degree carby wedge plates to level out the carby, but

I'm running a t350 atm and don't think that could handle so much angle, yet alone and manual gear boxes with all the oil down one end. What are is known out there for drive line angle setting, and as well offsetting the engine.

I was looking to offset it 10mm to the passenger side, but when I look at cars with notable off set, I cringe as the machinist in me wants its all bang on!!. some bonnets its not noticeable, but I have a raised section that will make it noticeable.

I fully understand setting the diff to gear box angles, and that also if I run an excessive angle the small pinion bearing will also probably starve a little on oil.

[mgtstumpy]

The centre-line of engine/trans/differential must be parallel to centre-line of car. The pinion angle (Up) should equal trans angle (Down) with centre-lines being parallel when viewed from side on and above. Too steep an angle will affect affect the longevity of the uni-joint and lead to premature failure in addition to strange harmonics. Correct angle will prevent brinelling of the bearings The driveshaft needs to also be the correct diameter to match length (Critical speed). If you offset to LHS, centre-line of engine/trans MUST remain parallel to car centre-line. This isn't an issue as early Corvettes and Mustangs had engine offsets to RHS to clear steering shafts from column to steering box / R&P. Even with 4WD (Early Toyota LC), even with the offset pinion, the engine/trans/differential were parallel to centre-line.

[jeffa]

Why does it sit at 12 degrees? Is there something that the sump needs to clear? Maybe a different sump?

[Tappet Head]

plenty of room down stairs, I can drop the engine out threw the rails, The issue is the rails and transmission location, as I need the front up for header and steering clearance but the rear down to get it under the cross member and have some form of cabin space.

I have since cut out the cross member, raised the rear and change it back to 4 degrees, but lost me cabin space.

I'm setting it all up parallel to the center line, in the horizontal plane, the vertical plane the car motor is set at 4 degrees. atm the motor and box are on the center line,

[FRANK BASILE]

An interesting topic. Bought back some angst I faced with the 49 Ford F1. This had 50mm " raising Blocks" between the diff pads and springs [trucks have the diff below the springs] I removed them and caused mayhem, the driveshaft angles were way out. What happened was that whoever built this in the US had used a later F100 DIFF. I assumed from the way the pinion was pointing up it was a 4wd housing. They then fitted a 350/350 combo and aligned all to suit. I ended up removing and replacing the diff pads with a more conventional angle and refitted the engine /trans lower .